Real-time physical random bit generation at Gbps based on random fiber lasers.

We demonstrate for the first time, to the best of our knowledge, a high-speed physical random bit generator at gigabits/second without the time-delay signature based on chaotic power fluctuations of a random fiber laser. The random fiber laser is configured using a ring structure with semiconductor optical amplifiers as the optical gain and a fiber random grating as the random feedback medium. The long-length ring cavity provides a large number of densely spaced cavity modes that co-exist within the gain bandwidth tailored by the optical filter. Unlike fixed cavity modes in conventional fiber ring lasers, these modes are less phase-correlated due to the random distributed feedback from the fiber random grating fabricated by a plane-by-plane inscription technique without phase control, leading to intensified lasing output fluctuations with high-dimensional chaotic dynamic natures without specific cavity features, when the random fiber laser is operated slightly above the lasing threshold. Random bit generation at a bit rate up to ∼1.6  Gbps is achieved with verified randomness through standard tests. Different from the previously reported schemes requiring offline post-processing procedures, this physical random number generator can function in real time, offering high-quality randomness and security assurance for pertinent applications.